## Animal is-a object (yes, sort of confusing) look at the extra credit
class Animal(object):
    pass
## ??
class Dog(Animal):
    
    def __init__(self, name):
        ## ??
        self.name = name
## ??
class Cat(Animal):
    def __init__(self, name):
        ## ??
        self.name = name
        
## ??
class Person(object):
    def __init__(self, name):
        ## ??
        self.name = name
        
        ## Person has-a pet of some kind
        self.pet = None
        
## ??
class Employee(Person):
    def __init__(self, name, salary):
        ## ?? hmm what is this strange magic?
        super(Employee, self).__init__(name)
        ## ??
        self.salary = salary
        
## ??
class Fish(object):
    pass
    
## ??
class Salmon(Fish):
    pass
    
## ??
class Halibut(Fish):
    pass
    
## rover is-a Dog
rover = Dog("Rover")
## ??
satan = Cat("Satan")
## ??
mary = Person("Mary")
## ??
mary.pet = satan
## ??
frank = Employee("Frank", 120000)
## ??
frank.pet = rover
## ??
flipper = Fish()
## ??
crouse = Salmon
## ??
harry = Halibut() 
2019-10-01
23:51:14
Exercise 42 - class and instantiate
原文:https://www.cnblogs.com/petitherisson/p/11615821.html